Transmitter-receiver system

ABSTRACT

A transmitter-receiver system is based upon electrically heated bimetal contactors. The transmitter is percentage on timer that responds to a sensed condition, while the receiver bimetal takes a position that is a function of the percentage on time. The heaters for both transmitter and receiver are connected in series so that fluctuations in supply voltage are compensated. Changes in ambient temperature at either transmitter or receiver or both may be compensated by means of compensating bimetals.

United States Patent Sweger [54] TRANSMITTER-RECEIVER SYSTEM 2,254,112 8/1941 Werner ..3l8/221H us] 3,662,241 51 May 9,1972

2,874,344 2/1959 Slocum ..3l8/473X 3,258,647 6/1966 Clark ..3l8/473X Primary Examiner-Benjamin Dobeck Attorney-A. Richard Koch [57] ABSTRACT A transmitter-receiver system is based upon electrically heated bimetal contactors. The transmitter is percentage on timer that responds to a sensed condition, while the receiver bimetal takes a position that is a function of the percentage on time. The heaters for'both transmitter and receiver are connected in series so that fluctuations in supply voltage are compensated. Changes in ambient temperature at either transmitter or receiver or both may be compensated by means of compensating bimetals.

ll Claim, 6 Drawing Figures P'A'TE'N'TEUMM 9 1912 I 3, 662 241 INVENTOR RUJSELL P. 5W6R AGENT PATENTEDMAY 91972 3.662.241

SHEET 2 OF 2 INVENTOR RUJSELL P. 514 5651? AGENT BACKGROUND OF THE INVENTION This invention pertains especially to servo controls whereby a driven device is moved in either direction and stopped in the fault is found and corrected, or it may. result in improper operation of the control and the destruction of the control, the controlled device, or somethingacted upon by the controlled device. Often faulty wiring is difficult to locate even though it Is may involve only the transposition oficonnections. Itis therefore desirable to design controls so that only one connection must be made during installation, or so that, if more than one connection must be made, the connectionsmay any combination without causing malfunction.

Other problems with controls are due to variations in voltage supplied thereto, the lengths of wire required to interconnect the various components, the difference in ambient tem peratures at the respective components and the ever present problem of cost in manufacture and installation.

SUMMARY This invention covers a transmitter-receiver control system useful for positioning a reversible driven device as a function of a variable condition. The transmitter providesa time proportionedon-off electric signal to the receiver as a functionof thevariable condition. The receiver takesa position as a function of the time proportioned signal. In one position the receiver completes an energy path causing movement by a controlled motor in one direction. In another position the receiver completes an energy path causing movement by the motor in opposite direction. The system is dependent upon current in a series circuit and so is independent of voltage fluctuations and the length of wire required to interconnect the transmitter, receiver and source of current. The order of connection in series of the transmitter,receiver and source of current makes no difference and transposition of the'wires at any component in the series circuit will have no effect on operation of the control. the current supplied may be of either polarity or alternating in direction. Ambient compensation is provided at the transmitter, the receiver, or both as required.

Thesystem is simple, easily calibrated and adjusted, and inexpensive compared to other controls providing similar features.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic wiring diagram of a thermostat controlling by an alternating current the operation of a reversible shaded pole motor.

FIG. 2 is a schematic wiring diagram of a pressure responsive transmitter controlling by a direct current signal the gat- .ing of solid state bidirectional switches to control operation of a permanent split capacitor motor.

FIG. 3 is a schematic wiring diagram of a cam responsive transmitter controlling operation of a series direct current or universal motor.

FIG. 4 is a schematic wiring diagram of a winter-summer changeover thermostat controlling the switching of transistors to control operation of a direct current shunt motor.

FIG. 5 is a schematic wiring diagram of an electrical signal responsive transmitter controlling by an alternating current signal the flow of air from the nozzles of bleed valves exercising authority over a double-acting piston and cylinder pneumatic motor.

FIG. 6 shows an alternate construction for one of the thermostatic switches.

bemade in DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the invention shown and described herein are merely examples of its many applications and do not define the scope of the invention which is limited only by the claims.

The servo motor control system seen in FIG. 1 comprises a transmitter l, a receiver 2, a source'of electric current 3, a reversible motor 4, and an alternating current power supply 5. In the transmitter l, a thermostatic device 7, shown and hereafter described as if it were a bimetal with a high expansion side H and low expansion side L, has one end 8 mounted upon a stationary support 9 such that the bimetal is exposed to ambient temperature. A contact 10, shown as mounted on the high expansion side I! at the free end 11 of the bimetal 7, is movable by the bimetal in response to changes in ambient temperature. A second contact 12 is adjustably mounted on athe adjustable contact 12 and at the other end by conductor 18 to the source of electric current 3, shown as a source of altemating current although it could as well be direct current. A resistance heater 20 in the receiver 2 is connected by conductor 21 to the source of current 3 and by conductor 22 to the movable contact 10. For convenience the conductor 22 is connected to the mounted end 8 of bimetal 7 upon which the contact 10 is mounted, so that the bimetal serves the double function both as a means for moving the contact 10 and a thermostatic device. i

It will be seen that thetransmitter l is a thermostat and that, when the ambient temperature falls to the setpoint indicated by the position of the dial l5 withrespect to the pointer 16, the bimetal 7 will be deformed and deflected upwardly to close the pair of contacts l0, l2 and so complete a series heating circuit from the source of current 3 through conductor 18, heater 17, contacts 12 and I0, bimetal 7, conductor 22, heater 20 and conductor 21 back to current source 3. The resulting current will generate heat in both heaters 17 and 20 as long as the contacts 10 and I2 are closed. Heat generated in heater 17 will be transferred to the bimetal 7, raising its temperature above ambient and causing it to deflect downwardly until con 'reclose contacts 10 and 12. In orderto raise the setpoint temperature, the dial 15 is rotated with respect to pointer 16 in a direction such that the screw 14 advances through the fixed support 13 and moves the adjustable contact 12 towards movable contact 10, requiring less upward deflection of bimetal 7 to close the contacts 10 and 12. Rotation of dial 15 in the opposite direction causes the screw 14 to move backward through support 13 and move theadjustable contact 12 away from movable contact 10, requiring more upward deflection of bimetal 7 to close the contacts 10 and 12. With a predetermined setpoint, the heat transferred from the heater 17 to the bimetal 7 must be increased as the ambient temperature falls further below setpoint in order to open the contact pair l0, l2 and less time will be required to cool the bimetal 7 to setpoint temperature after the heating circuit, has been broken by separation of the contacts 10 and 12. Since opening and closing of the contacts 10 and 12 is rapidly repeated, the result is a time-proportioned on-off current in the heating circuit with the ratio of on-to-off times increasing as the ambient temperature falls and decreasing as the ambient temperature rises.

In the receiver 2 a heated thermostatic device 23, shown and hereafter described as a bimetal with a high expansion side H and a low expansion side L, has a free end 24 and an end 25 rotatable about a fixed pivot 26, said bimetal being in heat transfer relation to the heater 20. A similar compensating thermostatic device 27, shown and hereafter described as if it were a bimetal with a high expansion side H and a low expansion side L, is fixedly mounted at one'end 28 with respect to the mounted end 25 so that the other end 29 of the bimetal 27 is adjacent to the free end 24 of bimetal 23. The end 29 is adjustable restrained, as shown by a tension spring 30 and an adjusting screw 31, with respect to a fixed support 32, whereby the free end 24 can be set in'a predetermined position through rotation of the bimetals 23 and 27 as a unit around the fixed pivot 26 as the screw 31 is advanced or retracted with respect to the fixed support 32, the spring 30 biasing the restrained end 29 toward the screw 31. A contact 33, shown as mounted on the high expansion side H of the bimetal 23 at the free end 24, is movable into and out of engagement with a stationary contact 34 by deflection of bimetal 23 or by adjustment of the position of the bimetal by means of screw 31, as described above. Another contact 35, facing oppositely to contact 33, is likewise movable into and out of engagement with a stationary contact 36. The high expansion side H of both bimetals 23 and 27 face in the same direction (upwardly as shown) so that since both bimetals deflect in the same direction and by the same amount due to ambient temperature, the position taken by the contacts 33 and 35 with respect to the contacts 34 and 36 will be independent of ambient temperature.

The reversible motor 4 shown in FIG. 1 is a reversible shaded pole motor having a rotor 38, a primary winding 39 connected across the AC power supply 5, a forward shading winding 40 connected between the forward control contacts 33 and 34, and a reverse shading winding 41 connected between the reverse control contacts 35 and 36. As shown a conductor 42 joins the stationary contact 34 to the forward shading winding 40, a conductor 43 joins the stationary contact 36 to the reverse shading winding 41, and a conductor 44 and the bimetal 23 form a common path from the shading windings 40 and 41 to the movable contacts 33 and 35.

The adjusting screw 31 is advanced through the fixed support 32 to move contact 33 into engagement with the stationary contact 34 when the bimetal 23 is at ambient temperature. When these forward control contacts 33, 34 are closed, a forward energy path or circuit is completed from the forward shading winding 40 through common conductor 44, bimetal 23, the forward control contacts 33 and 34, and conductor 42 back to the shading winding 40, in which current is induced by transformer action from the primary winding 39. When current is induced in the forward shading winding 40, the rotor 38 revolves in what we shall refer to as forward direction. If heat is transferred from the heater 20 to bimetal 23, the free end 24 is deflected downwardly, separating the contacts 33 and 34 to break the forward energy circuit and stop forward rotation of the rotor 38. If sufficient heat is transferred from heater 20 to the bimetal 23, the free end 24 will be deflected enough to close the reverse control contacts 35 and 36. When contacts 35 and 36 are closed, a reverse energy path or circuit is completed from the reverse shading coil 41 through common conductor 44, bimetal 23, contacts 35 and 36, and conductor 43 back to shading winding 41, in which current is induced to produce rotation of the rotor 38 in reverse direction. When the heater 20 ceases to produce heat, the bimetal 23 cools, causing the free end 24 to deflect upwardly and separate contacts 35 and 36, breaking the reverse energy circuit and stopping reverse rotation of the rotor 38.

Rotation of the rotor 38 is employed to produce corrective action to bring the temperature being sensed by the bimetal 7 in transmitter l to the setpoint established by the setting of the dial 1 with respect to the pointer 16. With contacts 33 and 34 initially closed the rotor 38 will revolve in forward direction to progressively close a valve or damper (not shown) supplying heat to the controlled space. When heat is required contacts and 12 close, permitting generation in heaters 17 and of heat tending to open both pairs of contacts 10, 12 and 33, 34. When contacts 33 and 34 open, rotation of the rotor in forward direction ceases and the valve or damper remains in the existing position, providing heat to the conditioned space at a steady rate. Upon more heat being transferred to the bimetal 23, the reverse control contacts 35 and 36 will be closed, producing reverse rotation of the rotor 38 to provide a progressive opening of the valve or damper with a resulting increased flow of heat to the controlled space. Since the on-off time-proportioned current passed by the contacts 10, 12 will decrease in effective value as the temperature sensed by the bimetal 7 approaches the setpoint temperature, the temperature of the bimetal 23 will be reduced and the position of the free end will gradually rise, breaking the reverse energy circuit and stopping reverse rotation of the rotor 38. This will stop movement of the driven valve or damper in the existing position. If the heat generated in heater 20 is further reduced, contacts 33 and 34 will be closed causing the damper or valve to be further closed by reverse rotation of the motor 5.

Since the heating circuit is series connected, all of the current in the circuit, generally speaking, passes through each of the components therein, making the order in which they are connected in the circuit of no importance. Since it is a heating circuit and heat is generated by any type of electric current through a resistance, the source of current 3 could deliver alternating or direct current and, if direct current, of either polarity. If the current in the heating circuit were to increase, the heat required to open contacts 10 and 12 would be generated in less time, but cooling time would be unaffected, resulting in a shorter on-to-off ratio. The higher current flowing for the lesser time would generate the same heat in heater 20 as the lesser current flowing for a greater time and have no effect upon the heat transferred to bimetal 23 or upon the position of the latter. The lengths of the conductors 18, 21 and 22 affect the resistance of the circuit, an increase in length increasing the circuit resistance and so decreasing the current. As noted above a change in current in the circuit in no way affects its operation if the current remains sutficiently high to generate the heat required for operation of the system.

In FIG. 2 the same reference numerals are used to identify like components, which will not be described again. A source of direct electric current 3a, shown as a battery, has been substituted in the series heating circuit. Direct current is desirable for the heating circuit, especially on long runs between the transmitter, receiver and source of current, because it reduces the shunting effect of capacitance and inductance between the conductors.

The transmitter 1a in FIG. 2 is a pressure sensitive control with the mounted end 8 of bimetal 7 rotatable around a fixed pivot 46. A compensating bimetal 47 with a high expansion side H and a low expansion side L is fixedly mounted at one end 48 with respect to the mounted end 8, while the other end 49 is adjacent the free end 11 and movable by a pressure expansible bellows 50 in opposition to a biasing compression spring 51 abutting a fixed support 52. Fluid pressure P may be delivered to or exhausted from the bellows 50 through a conduit 53. The bimetals 7 and 47 have their high expansion sides H facing in the same direction (upwardly, as shown) so that both are deflected in the dame direction and by the same amount in response to changes in ambient temperature. The relationship between the contacts 10 and 12 is therefore independent of ambient temperature. An increase in pressure P moves the movable contact 10 toward, and a decrease moves it away from, the adjustable contact 12. The pressure setpoint is established by advancing or retracting the screw 14 in fixed support 13. Heat transmitted from heater 17 causes bimetal 7 to bow concave downward, moving contact 10 out of engage-- ment with contact 12 and soopening the heating circuit, after which cooling of the bimetal moves contact 10 back into engagement with contact 12 to reclose the heating circuit. Once again an on-off time-proportioning current signal is passed to the heaters 17 and 20.

The receiver 2a in FIG. 2 discloses the end 24 of heated bimetal 23 restrained between an adjusting screw 55 and a biasing compression spring 56 with advancement or retraction of adjusting screw 55 causing rotation of both bimetal 23 and 27 around fixed pivot 26 and downward or upward movement of the free end 29. Deflection due to heating of bimetal 23 will result in counterclockwise rotation of bimetal 27 and upward movement of the free end 29, while cooling of bimetal 23 will result in downward movement of the free end 29 caused by clockwise rotation of the compensating bimetal 27 around the fixed pivot 26. A contact 57, shown'as attached to the high expansion side H at the free end 29 of compensating bimetal 27, is movable by bimetal 27 into and out of engagement with a stationary contact 58. Another contact 59, shown as attached to the low expansion side L at the free end 29, is movable by bimetal 27 into and out of engagement with an adjustable contact 60, movable by an adjusting screw 61 to control the deadband between forward and reverse motions of the motor 4a. The adjusting screw 55 is retracted so that contact 59 engages adjustable contact 60 when the heated bimetal 23 is at ambient temperature. As bimetal23 is heated by the heater 20, its temperature rises causing it to bow concave downwardly to rotate compensating bimetal 27 around pivot 26 and lift contact 59 out of engagement with contact 60. Upon further heating of bimetal 23, contact 57 engages contact 58.

The motor 4a is a reversible permanent split capacitor motor, having a rotor 38, a first winding 63, a second winding 64, and a capacitor 65, said first and second windings and said capacitor being connected in a closed series loop. A bidirectional controlled switch, shown as a Triac 66, is connected between a junction 67, joining the winding 63 to capacitor 65, and a terminal 68 at one side of the altemating current power supply 5. Another bidirectional controlled switch, shown as a Triac 69, is connected between a junction 70, joining the winding 64 to capacitor 65, and the terminal 68. The junction 71, joining the windings 63 and 64, isconnected to the other side of power supply 5. Junction 71 is also connected through conductor 72 and a current limiting resistor 73 to bimetal 27. A gating terminal 74 of Triac 66 is connected to the adjustable contact'60, and gating terminal 75 of Triac 69 is connected to the stationary contact 58.

With contacts 59 and 60 closed, a forward gating circuit is completed from power supply 5 through Triac 66 from terminal 68 to gating terminal 74, contacts 60 and 59, bimetal 27, resistor 73, and conductor 72 back to the power supply 5. Completion of this circuit'gates the Triac 66 into conduction and completes a forward energizing circuit from power supply 5 through the Triac 66 from terminal 68 to junction 67, a first branch circuit comprising winding 63 and a parallel second branch circuit comprising capacitor 65 in series with winding 64, and junction 71 back to powersupply 5, permitting the rotor 38 to revolve in a forward direction. Similarly when contacts 57 and 58 are closed, a reverse gating circuit is completed from power supply 5 through Triac 69 from terminal 68 to gating terminal 75, contacts 58 and 57, bimetal 27, resistor 73, and conductor 72 back to the power supply 5. Completion of this circuit gates the Triac 69 into conduction and completes a reverse energizing circuit from power supply 5 through the Triac 69 from terminal 68 to junction 70, a third branch circuit comprising winding 64 and a parallel fourth branch circuit comprising capacitor 65 in series with winding 63, and junction 71 back to the power supply 5, permitting the rotor 38 to revolve in reverse direction. When neither set of contacts 57, 58 nor 59, 60 is closed, neither of the energizing circuits is completed and the rotor 38 is not driven in either direction. The use of bidirectional controlled switches or other type of relay to open and close the energizing circuits increases life of the contacts in the receiver, especially when the entire motor current must be controlled as in the permanent split capacitor motor 4a. If electromagnetic relays are employed, the gating circuits may be electrically isolated from the energizing circuits provided a separate source of power is utilized for the gating circuits. By employment of multipole relays control may be exerted over three phase motors. The use of relays also permits greater separation of the receiver 2a from the motor 4a.

It will be obvious to those skilled in the art that if ambient temperature at both the transmitter la and receiver 2a are held steady, the compensating bimetals 27 and 47 could be eliminated and heat insensitive arms substituted for them.

According to FIG. 3 the transmitter lb has a compensating bimetal 77 extending from pivot 46 in opposite direction from heated bimetal 7 and with its high expansion side H facing in opposite direction from the high expansion side H of bimetal 7. Changes in ambient temperature will cause equal and opposite deflections of the bimetals so that the relative positions of contacts 10 and 12a are unaffected by changes in ambient temperature. The end 78 is shown as restrained between a setpoint screw 79 and a biasing compression spring 80, which together establish the free position of contact 10 when no heat is transmitted to bimetal 7. The heater 17a is wound directly on the heated bimetal 7 to obtain the best possible heat transfer between them. Contact 12a is movable by a cam 81 toward contact 10 and by biasing compression spring 82 away from the contact 10. As shown the contact 12a is attached to a cantilevered beam 83, upon which the cam 81 and biasing,

spring act. This transmitter 1b is especially adapted for use in positioning systems.

The receiver 2b discloses the end '29 of compensating bimetal 27 held in fixed position between stops 85 and 86. Adjustment is achieved by repositioning the adjustable contacts 87 and 88, engageable with the moving contacts 33 and 35 respectively. The contacts 87 and 88 are shown mounted in fixed spaced opposition on an arm 89 rotatable about a fixed pivot 90 by an adjusting screw 91 and an opposed biasing spring 92.

The motor 4b is a reversible universal or series wound direct current motor having a wound armature or rotor 38a with brushes 93 and 94 conducting current thereto, a forward series field winding 95, and a reverse series field .winding 96. The forward winding 95 is connected between the adjustable contact 87 and brush 94, and the reverse winding 96 is connected between the adjustable contact 88 and brush 94.

The power supply 5a may furnish either alternating or direct current. It is connected to the brush 93 by a conductor 97.

When forward control contacts 33 and 87 are closed, a forward energizing circuit is completed from power supply 511 through conductor 44, bimetal 23, contacts 33 and 87, forward winding 95, brush 94, armature 38a, brush 93, and conductor 97 back to power supply 5a, enabling the armature or rotor 38a to rotate in forward direction. When reverse control contacts 35 and 88 are'closed, a reverse energizing circuit is completed from power supply 5a through conductor 44, bimetal 23, contacts 35 and 88, reverse winding 96, brush 94, armature 38a, brush 93, and conductor 97 back to power supply 5a, enabling the armature or rotor 38a to rotate in reverse direction. If neither pair of contacts 33, 87 nor 35, 88 is closed the motor 4b will not be energized and the rotor 38a will not be driven in either direction. The heating circuit operates in the same manner as previously described.

In FIG. 4 the transmitter 10 is a winter-summer changeover thermostat for use in a heating and cooling system in which a single pipe or duct delivers either hot or chilled fluid to the controlled space. A thermostatic bimetal 99, having a high expansion side H and a low expansion side L is mounted in cantilever fashion on a support 100 rotatable by a gear sector 101, adjusted by a worm gear 102 in response to movement of dial 15 with respect to the pointer 16. On the free end 103 of bimetal 99 is an extension 104 of a more active bimetal having its high expansion side H and low expansion side L facing in the same direction as their counterparts in bimetal 99. A contact 105, movable by the free end 106 of extension 104 on tl'i I high expansion side H thereof, is engageable with a stationary contact 107. A rearwardly extending arm 108, cantilevered from the free end 106 on the low expansion side L thereof, has a free end 109 adapted to move a contact 110 into and out of engagement with a stationary contact 111. Contacts 107 and 111 are connected to respective winter contact 112 and summer contact 1 13 of a double throw winter-summer switch 114, and the common terminal 115 of which is connected to a gate terminal 116 of a bidirectional controlled switch 117,

hereinafter referred to as a Triac. The Triac 117 when gated the delivery of hot or cold fluid to the conditioned space. The

heater 17 is located in heat transfer relation to the extension bimetal 104. The contacts 105 and 110 are shown connected to conductor 22 through the bimetal 99 and the extension 104 thereon. It will be seen that the Triac 117 could be eliminated by connecting the heater 17 between the common terminal 115 and conductor 18. The use of the Triac increases the life of contacts 105, 107, 110 and 111 and permits use of a smaller switch 1 14.

During the heating season, the common terminal 115 is connected through the winter-summer switch 114 to the winter contact 112. When the ambient temperature falls below the setpoint established by the position of the dial with respect to pointer 16, contact 105 is moved into engagement with stationary contact 107, completing a winter gating circuit from the source of alternating current 3 through conductor 21, heater a, conductor 22, bimetal 99, extension 104, contacts 105 and 107, switch 114 from winter contact 112 to common terminal 115, Triac 117. from gate terminal 116 to conductor 18, and conductor 18 back tov the source of current 3. Completion of the gating circuit gates the Triac .117 into conduction, completing the heating circuit previously described and so generating heat in heater 17 to open the contacts 105 and 107, terminating the gating current and breaking the heating circuit as explained in detail with regard to FIG. 1. During the cooling season, the common terminal 115 is connected through the switch 114 to the summer contact 113. When the ambient temperature rises above setpoint, bimetal 99 and its extension 104 deflect downwardly to move contact 110 into engagement with the stationary contact 111 and complete a summer gating circuit from the source of alternating current 3 through conductor 21, heater 20a, conductor 22, bimetal 99, extension 104, arm 108, contacts 110 and 111, switch 114 from summer contact 113 to common terminal 115. Triac 117 from gate terminal 116 to conductor 18, and conductor 18 back to the source of current 3. The heating circuit is the same as during the heating season.

When the heating circuit is closed heat generated in heater 17 is transmitted to the extension bimetal 104, causing the extension to bow concave downward to a greater extent, resulting in a reverse upward movement'of the end 1090f rearwardly extending arm 108, separating contact 110 from contact 111 and opening the summer gating circuit. Opening of the gating circuit breaks the heating circuit to heaters 17 and 20a. When extension bimetal 104 no longer receives heat from heater 17, it cools and returns to the shape it had before being heated, causing the arm 108 to move contact 110 downwardly again into engagement with contact 111.

A Triac is limited to use with alternating or pulsating current sources because it only turns off when the current through it drops to zero. A properly poled transistor could be substituted for the Triac 117 for use with a direct current source and various types of relays could be substituted for use with either alternating or direct current sources.

In receiver 2c compensating bimetal 27 is mounted in cantilever fashion at end 29 on a fixed support 119 and is rigidly connected at end 28 to end 25 of heated bimetal 23. The movable contacts 33 and 35 may be selectively engaged with respective adjustable contacts 120 and 121, separately and respectively positioned by adjusting screws 122 and 123. The heater 20a is shown as wound on heated bimetal 23.

The motor 40 is a reversible shunt wound DC motor having an armature or rotor 38a with brushes 125 and 126 delivering current thereto, a forward shunt field winding 127 and a reverse shunt field winding 128. The brush 126 and one end each of the shunt windings 127 and 128 share a common connection 129 to the positive terminal of a direct current power supply 5a, shown as a battery. The other ends of windings 127 and 128 are connected respectively through collector-emitter circuits of transistors 130 and 131 to brush and through conductor 132 to the negative terminal of power supply 5a. The bases of transistors and 131 are respectively connected to adjustable contact 120 and 121. The common connection 129 is joined with movable contacts 33 and 35, as shown through a current limiting resistor 133 and bimetals 27 and 23.

Once again, due to the compensating bimetal 27, the contacts 33 and 35 are moved only in response to the heating of heated bimetal 23 by the heater 20a. At ambient temperature, bimetal 23 maintains contact 33 in engagement with contact 120, closing a forward switching circuit from the positive terminal of battery 5a through common connection 129, resistor 133, bimetals 27 and 23, contacts 33 and 120, the baseemitter circuit of transistor 130, and conductor 132 to the negative terminal of battery 5a, switching transistor 130 into conduction. The conducting transistor 130 completes a forward energy circuit from the positive terminal of battery 5a through common connection 129, forward shunt winding 127, the collector-emitter circuit of transistor 130 and conductor 132 to the negative terminal of battery 5a, energizing the forward shunt winding 127. The armature of rotor 38a is continuously energized by an armature circuit from the positive terminal of battery 5a through common connection 129, brush 126, armature 38a, brush 125 and conductor 132 to the nega tive terminal of battery 5a, so that when the forward shunt winding 127 is energized the armature is driven in forward direction. As the heated bimetal 23 is heated by heater 20a, contact 33 is separated from contact 120 and the forward switching circuit is broken, switching the transistor into nonconducting state and so deenergizing the forward shunt winding 127 to stop rotation of the armature 38a. Upon further heating of the bimetal 23, contact 35 is moved to engage contact 121, closing a reverse switching circuit from the positive terminal of battery 5a through common connection 129, resistor 133, bimetals 27 and 23, contacts 35 and 121, the baseemitter circuit of transistor 131, and conductor 132 to the negative terminal of the battery 5a, switching transistor 131 into conduction. The conduction transistor 131 completes a reverse energy circuit from the positive terminal of battery 5a through common connection 129, reverse shunt winding 128, the collector-emitter circuit of transistor 131, and conductor 132 to the negative terminal of battery 5a, energizing the reverse shunt winding 128 and so driving the armature in reverse direction. When the heat produced in heater 20a is reduced, the heated bimetal cools, separating the contacts 35 and 121 and breaking the reverse switching circuit. This in turn deenergizes the reverse shunt winding 128 to stop rotation of the armature 38a. A single shunt winding should be employed by reversing direction of current therethrough by use of double pole relays energized by the switching circuits.

In FIG. 5 the transmitter responds to an electrical signal and the transmitter controls a pneumatic double acting piston and cylinder engine or motor. The transmitter 1d is similar to la in FIG. 2, differing in that the end 49 is adjustably restrained by a pair of spaced abutments 135 and 136, movable about a fixed pivot 137 by an adjusting screw 138 and an opposed biasing spring 139. A resistance heater 140 generates heat as a result of an electric current input thereto from a source not shown. The heater 140 is positioned to transfer heat to the bimetal 47, which bows concave downward when heated, causing bimetal 7 to rotate about pivot 46 and move contact 10 into engagement with contact 12 to close the heating circuit. Heat generated in heater 17 as a result of closure of the heating circuit causes bimetal 7 to bow concave downward and separate contacts 10 and 12 to break the heating circuit.

The receiver 2d is similar to 2 in FIG. 1. A second heater 142 has been added in heat transfer relation to bimetal 27. An adjusting cam 143 has been substituted for the screw 31 and a compression spring 144 for tension spring 30. The movable contacts 33 and 35 have been eliminated and nozzles 145 and 146 have replaced stationary contacts 34 and 36, the end 24 of bimetal 23 acting as a flapper controlling bleed of air from the nozzles 145 and 146.

Air under pressure is delivered from mains 147 and 148 through orifices 149 and 150 to chambers 151 and 152 respectively. A branch 153 leads from chamber 151 to the upper portion 154 (above piston 155) of cylinder 156. A branch 157 leads from chamber 152 to the lower portion 158 (below piston 155) of cylinder 156. The piston 155 of cylinder 156 comprise a reversible double-acting engine or motor 4d, delivering power through a reciprocating piston rod 159 to an external load not shown;

A double throw direct-reverse action changeover switch 161 has its direct action contact 162 connected to heater 20, its reverse action contact 163 connected to heater 142, and its common terminal 164 connected to the source of current 3.

For direct action the common terminal 164 is connected to the direct action contact 162 through switch 161. When the contact pair 10, 12 in transmitter 1d closes, a direct action heating circuit is completed from source of current 3 through conductor 18, bemetal 7, contacts and 12, heater 17, conductor 22, heater 20, switch 161 from direct action contact 162 to common terminal 164, and conductor 21 back to source of current 3. Heat transferred from heater causes bimetal 23 to bow concave downward, moving flapper end 24 away from nozzle 145. If we assume that flapper 24 was initially in contact with nozzle 145, preventing bleed of air therethrough, air delivered from main 147 through orifice 149 into chamber 151 would flow through branch 153 into the upper portion 154 of cylinder 156, building up pressure therein and forcing piston 155 and piston rod 159 downward, or in forward direction. When the flapper 24 moves away from nozzle 145, as described above, permitting air to bleed therethrough, air under pressure in the upper portion 154 of cylinder 156 flows through the branch 153 into chamber 151, from which it is exhausted through the open nozzle 145. This reduces the pressure above piston 155 and permits upward movement of piston 155 and piston rod 159. if the flapper 24 is deflected far enough to close the nozzle 146, preventing air from bleeding therethrough, air delivered from main 148 through orifice 150 into chamber 152 would flow through branch 157 into the lower portion 158 of cylinder 156, building up pressure therein and forcing piston 155 and piston rod 159 upward, or in reverse directiomWhen contact pair 10 and 12 is opened, breaking the direct action heating circuit, heat is no longer transferred from heater 20 to bimetal 23, permitting the latter to cool and return toward its initial shape, moving the flapper 24 upwardly away from nozzle 146. When flapper 24 opens nozzle 146, permitting air to bleed therethrough, air under pressure in the lower portion 158 of cylinder 156 flows through the branch 157 into chamber 152, from which it is exhausted through the open nozzle 146. This reduces the pressure under piston 155 and permits downward movement of the piston 155 and piston rod 159. Ordinarily the mains 147 and 148 deliver air from the same power supply (not shown), which would be an air compressor or other source of air under pressure. The forward energy path comprises the power supply, main 147, orifice 149, chamber 151, branch 153 and the upper portion 154 of cylinder 156, while the reverse energy path comprises the power supply, main 148, orifice 150, chamber 152, branch 157, and the lower portion 158 of cylinder 156. The bimetal 27 serves the compensating bimetal during direct action operation.

For reverse action the common terminal 164 is connected to the reverse action contact 163 through switch 161. When the contact pair 10, 12 closes, a reverse action heating circuit is completed from source of current 3 through conductor 18, bimetal 7, contacts 10 and 12, heater l7, conductor 22, heater 142, and switch 161 from reverse action contact 163 to common terminal 164, and conductor 21 back to the source of current 3. Heat transferred from heater 142 causes bimetal 27 to bow concave downward, rotating bimetal 23 counterclockwise around pivot 26 and moving flapper end 24 away from nozzle 146 and toward nozzle with the results described above with regard to the direct action operation. It will be noted, however, that motion of the piston rod 159 is reversed. When the contact 10 is separated from contact 12, the reverse action heating circuit is broken and heat is no longer transferred from heater 142 to bimetal 27, permitting the latter to cool and return toward its initial shape. This restoration causes bimetal 23 to be rotated clockwise around pivot 26 to move flapper end 24 away from nozzle 145 and toward nozzle 146, again with the results described with regard to the direct action operation, but with direction reversed. During reverse action operation the bimetal 23 serves as the compensating bimetal.

FIG. 6 shows an alternative construction for the bimetals. As shown it is equivalent to the bimetals in the receiver 2c in FIG. 4, with the bimetals 23 and 27 stamped from a single piece, being joined at ends 25 and 28, the flange 166 at the joined ends 25 and 28 preventing transverse deflection.

It will be obvious to those skilled in the art that the embodiments described, as well as others, of the transmitters could be combined with the embodiments described, aswell as others, of the receivers in different combinations, that subcombinations within the transmitters and receivers respectively could be interchanged, and that various types of motors could be controlled without departing from the spirit and intent of this invention. While only bimetallic thermostatic devices have been shown and described, it will be obvious that thermostatic bellows, rod and tube mechanisms and other means could be substituted therefor. Other motors such as heat motors and air turbines could be employed. Hydraulic motors could be controlled.

lclaim:

l. A transmitter-receiver system useful in a servocontrol for a reversible motor energizable from a power supply comprising a transmitter, a receiver, and a source of electric current, a pair of electrical contacts in said transmitter, means for moving one said contacts toward the other of said contacts in response to a variable condition, a first thermostatic device mounted in the transmitter, a first heater in heat transfer relation to said first thermostatic device, a second heater in the receiver, means for connecting said heaters, the pair of contacts and said source of electric current in series in any order to form a heating circuit for the heaters when the contacts are closed, said first thermostatic device deformable by heat from said first heater to open the contacts whereby an on-off time proportioned current signal is supplied to the second heater, a second thermostatic device mounted in said receiver in heat transfer relation to the second heater and deformed by heat from said second heater, a forward control means operable in a first position of the second thermostatic device to provide a forward energy path for said motor whereby the motor is enabled to produce a forward motion, and a reverse control means operable in a heat deformed position of the second thermostatic device to provide a reverse energy path for said motor whereby the motor is enabled to produce a reverse motion.

2. A transmitter-receiver system according to claim 1 wherein said thermostatic devices are bimetals.

3. A transmitter-receiver system according to claim 1 additionally comprising a third thermostatic device in said receiver compensating the second thermostatic device for changes in ambient temperature at the receiver.

4. A transmitter-receiver system according to claim 1 additionally comprising a third thermostatic device in said transmitter compensating the first thermostatic device for changes in ambient temperature at the transmitter.

5. A transmitter-receiver system according to claim 1 additionally comprising a third thermostatic device mounted in the receiver, a third heater in heat transfer relation to said third thermostatic device, and means for substituting the third heater for the second heater in said heating circuit.

6. A transmitter-receiver system according to claim 1 additionally comprising means for adjusting the relative positions of said contacts whereby the contacts are closed upon the occurrence of a predetermined measure of said variable condition.

7. A transmitter-receiver system according to claim 1 additionally comprising means for adjusting the relative positions of said second thermostatic device and the forward control means whereby said motor is enabled to produce forward motion when heat is supplied at a predetermined effective rate by said second heater to the second thermostatic device.

8. A transmitter-receiver system according to claim 1 additionally comprising means for adjusting the relative positions of said second thermostatic device and the reverse control means whereby said motor is enabled to produce reverse motion when heat is supplied at a predetermined effective rate by said second heater to the second thermostatic device.

9. A transmitter-receiver system according to claim 1 wherein one of said control means comprises a valve operable in one of the positions of said second thermostatic device to complete one of the energy paths for the motor.

10. A transmitter-receiver system according to claim 1 wherein one of said control means comprises a second pair of electrical contacts engagable in one of said positions of the second thermostatic device tocomplete one of said energy paths for the motor.

11. A transmitter-receiver system useful in controlling a variable condition comprising a transmitter, receiver, a source of electric current, a reversible motor, a power supply for said motor, and a device driven by the motor to control said'variable condition, a pair of electrical contacts in said transmitter, means moving one of said contacts toward the other of said contacts in response to'said variable condition, a first thermostatic device mounted in the transmitter, a first heater in heat transfer relation to said first thermostatic device, a second heater in the receiver, means for connecting said heaters. the pair of contacts and said source of electric current in series in any order to form a heating circuit for the heaters when the contacts are closed, said first theremostatic device deformable by heat from said first heater to open the contacts whereby an on-off time proportioned current signal is supplied to the second heater, a second thermostatic device mounted in said receiver in heat transfer relation to the second heater and deformed by heat from said second heater, a forward control means operable in a first position of the second thermostatic device to provide a forward energy path for said motor whereby the motor is enabled to produce a forward motion, a reverse control means operable in a heat deformed position of the second thermostatic device to provide a reverse energy path for said motor whereby the motor is enabled to produce a reverse motion, said motor by said forward and reverse motions positioning said driven device to bring the variable condition to a predetermined value.

i I. t l 

1. A transmitter-receiver system useful in a servocontrol for a reversible motor energizable from a power supply comprising a transmitter, a receiver, and a source of electric current, a pair of electrical contacts in said transmitter, means for moving one said contacts toward the other of said contacts in response to a variable condition, a first thermostatic device mounted in the transmitter, a first heater in heat transfer relation to said first thermostatic device, a second heater in the receiver, means for connecting said heaters, the pair of contacts and said source of electric current in series in any order to form a heating circuit for the heaters when the contacts are closed, said first thermostatic device deformable by heat from said first heater to open the contacts whereby an on-off time proportioned current signal is supplied to the second heater, a second thermostatic device mounted in said receiver in heat transfer relation to the second heater and deformed by heat from said second heater, a forward control means operable in a first position of the second thermostatic device to provide a forward energy path for said motor whereby the motor is enabled to produce a forward motion, and a reverse control means operable in a heat deformed position of the second thermostatic device to provide a reverse energy path for said motor whereby the motor is enabled to produce a reverse motion.
 2. A transmitter-receiver system according to claim 1 wherein said thermostatic devices are bimetals.
 3. A transmitter-receiver system according to claim 1 additionally comprising a third thermostatic device in said receiver compensating the second thermostatic device for changes in ambient temperature at the receiver.
 4. A transmitter-receiver system according to claim 1 additionally comprising a third thermostatic device in said transmitter compensating the first thermostatic device for changes in ambient temperature at the transmitter.
 5. A transmitter-receiver system according to claim 1 additionally comprising a third thermostatic device mounted in the receiver, a third heater in heat transfer relation to said third thermostatic device, and means for substituting the third heater for the second heater in said heating circuit.
 6. A transmitter-receiver system according to claim 1 additionally comprising means for adjusting the relative positions of said contacts whereby the contacts are closed upon the occurrence of a predetermined measure of said variable condition.
 7. A transmitter-receiver system according to claim 1 additionally comprising means for adjustinG the relative positions of said second thermostatic device and the forward control means whereby said motor is enabled to produce forward motion when heat is supplied at a predetermined effective rate by said second heater to the second thermostatic device.
 8. A transmitter-receiver system according to claim 1 additionally comprising means for adjusting the relative positions of said second thermostatic device and the reverse control means whereby said motor is enabled to produce reverse motion when heat is supplied at a predetermined effective rate by said second heater to the second thermostatic device.
 9. A transmitter-receiver system according to claim 1 wherein one of said control means comprises a valve operable in one of the positions of said second thermostatic device to complete one of the energy paths for the motor.
 10. A transmitter-receiver system according to claim 1 wherein one of said control means comprises a second pair of electrical contacts engagable in one of said positions of the second thermostatic device to complete one of said energy paths for the motor.
 11. A transmitter-receiver system useful in controlling a variable condition comprising a transmitter, receiver, a source of electric current, a reversible motor, a power supply for said motor, and a device driven by the motor to control said variable condition, a pair of electrical contacts in said transmitter, means moving one of said contacts toward the other of said contacts in response to said variable condition, a first thermostatic device mounted in the transmitter, a first heater in heat transfer relation to said first thermostatic device, a second heater in the receiver, means for connecting said heaters, the pair of contacts and said source of electric current in series in any order to form a heating circuit for the heaters when the contacts are closed, said first theremostatic device deformable by heat from said first heater to open the contacts whereby an on-off time proportioned current signal is supplied to the second heater, a second thermostatic device mounted in said receiver in heat transfer relation to the second heater and deformed by heat from said second heater, a forward control means operable in a first position of the second thermostatic device to provide a forward energy path for said motor whereby the motor is enabled to produce a forward motion, a reverse control means operable in a heat deformed position of the second thermostatic device to provide a reverse energy path for said motor whereby the motor is enabled to produce a reverse motion, said motor by said forward and reverse motions positioning said driven device to bring the variable condition to a predetermined value. 